Nyquist interval

Note 1: The Nyquist interval is equal to the reciprocal of twice the highest frequency component of the sampled signal.

Note 2: In practice, when analog signals are sampled for the purpose of digital transmission or other processing, the sampling rate[?] must be more frequent than that defined by Nyquist's theorem, because of quantization error introduced by the digitizing process. The required sampling rate is determined by the accuracy of the digitizing process.

Source: from Federal Standard 1037C and from MIL-STD-188